1. Field of the Invention:
The present invention relates to the fabricating of staircases and more particularly relates to a method and apparatus for fabricating custom staircases with selectively pre-spaced treads of preselected angular position that will define horizontal stair-step tread positions during use, wherein multiple tread work stations can be pre-spaced at regular intervals and each work station can support a tread adjacent a stringer at the desired angular orientation to that final connections by welding, for example, can be made.
2. General Background:
Staircases normally include one or more longitudinally extending members known as "stringers". The stringers support the horizontal part of the step in the staircase, known as the "tread". Stringers can be wood with the treads attached using tongue and groove connections, for example. Stringers can be metallic such as elongated beams of steel, aluminum, or the like with treads welded thereto, for example.
During the factory construction of staircases in a modular, high volume fashion, a problem arises in that each staircase to be manufactured may not be of the same dimension because of preexisting construction, and/or the custom needs of a particular home, building or structure. In such instances, the length and/or inclination of the stringers can change. Further the horizontal and vertical distances between the tread stair-step positions can vary. As a result, the angular intersection of the tread and stringer can vary from one staircase to the next. These changes in configuration can be minute from one manufactured staircase to the next, but a tread position change of even a few inches or a tread angular orientation of a few degrees eliminates the ability to repeatedly manufacture the same staircase in high volume without expensive custom carpentry, custom welding, or the like.
Various machines have been patented which related to machines that work metal, wood and work pieces with multiple material working stations. Applicant herein is the owner of U.S. Pat. No. 4,673,011, issued June 16, 1987, which related to a staircase stringer fabricating apparatus. The apparatus includes a structural machine frame having a carriage movably mounted with respect to the frame for supporting an elongated stringer work piece. A track mounted upon the structural frame defines a guide for the carriage so that the carriage can move on a controlled path with respect to the frame. Material working stations, such as wood routers, welding torches or the like, are spaced upon the machine frame for simultaneously preparing the work piece with selectively spaced-apart tread assembly portions that define a horizontal stair-step positions upon the stringer during use. The tread positions are preferably formed responsive to the movement of the carriage and work piece upon the track along the controlled path so that the work stations traverse the work piece. In the preferred embodiment, the wood routers simultaneously make cuts with equal separation in the wood stringer work piece to which individual treads can be affixed.
The present invention relates to an improvement over the apparatus disclosed in U.S. Pat. 4,673,011 in that a clamping mechanism associated with each of the plurality of work stations that support the treads in a position adjacent the stringer, in a variety of angular positions and at variable spacing so that both custom spacing and custom angular position of the treads is made at one time and simultaneously so that the entire stairway can be fabricated using welding, for example, while the treads and stringers are supported in the appropriate and desired custom position.
The Pearson U.S. Pat. No. 2,939,499 entitled "Automatic Machine For Routing Right and Left Hand Stair Stringers" provides an apparatus that uses a carriage upon which are mounted motors that are equipped with outers. The carriages are slideably moveable upon guide rails and powered by a fluid operative cylinder and piston. A mechanism is provided for adjusting the guide plates about their pivots for changing the riser-rung ratio for the stair stringers routed by the machine. The adjustment mechanism includes a block which slides a along a fixed guide extending from the back to the front of the main frame of the machine. A lead screw threads through the block and this lead screw is held against axial movement by a thrust bearing. The screw is rotated by applying a crank to the square end at the front of the machine. This apparatus requires an advancement of the stringer to each stair-step position so that the router can perform each of the multiple cuts as the stringer is advanced along its length, this is unlike the present invention wherein all the cuts are made while the work piece is held by the machine. Intervention by an operator to advance the stringer into multiple successive positions is not required. Additionally, the present invention can quickly adjust the spacing of the tread position on the stringer for each work piece, thus, custom staircases of variable dimensions and with variable tread spacing can be manufactured on a high volume basis.
Another patent showing material working machines using a plurality of work stations such as routers is the Onsrud U.S. Pat. No. 2,168,234 entitled "Grooving Machine".
Other patents, relating generally to fabricating devices are references which were cited during the prosecution of U.S. Pat. No 4,673,011 and include U.S. Pat. Nos. 769,931, issued to Baghurst; 1,352,196, issued to Hunter; 1,808,962, issued to MacKay; and 2,745,449, issued to Pearson.